1. Field of the Invention
This invention relates generally to the field of electronic communications. More particularly, the invention relates to electronic communication techniques for remote identification of objects.
2. Description of the Prior Art
In the field of electronic communications, a variety of remote interrogation techniques have been used to achieve positive identification of objects. Existing electronic interrogation techniques often consist of transmitting a radio-frequency (rf) signal that is intended to trigger a transponder or like device to elicit an electromagnetic reply. Such interrogation techniques have been used extensively by the military for identifying friendly forces and by aircraft controlers for identifyiny commercial aircraft.
More specifically, a typical military identification-friend-or-foe (IFF) system uses coded radio transmissions that friendly forces automatically respond to by emitting a coded response signal, which identifies them from enemy forces. A transmitter-receiver device, usually called an interrogator-responser or simply an interrogator, transmits the coded radio transmissions toward a target as an interrogation signal and receives the coded response signal. The equipment carried by the friendly forces usually includes a transponder having a circuit that is triggered by a received interrogation signal to automatically transmit the appropriate response signal, which positively identifies the target as being friendly.
In addition to IFF systems, achieving remote positive identification of objects is also becoming an important problem in such diverse areas as inventory control, physical security and retail pricing. For example, the inability to accurately make positive identification of objects can cost industry dearly by loses due to pilferage and theft, or because of increased inventory control costs. In this regard, warehousing requires at least two-dimensional, often three-dimensional placement of supplies. Categorizing regions of a warehouse usually allows simpler location and control of items, but does not necessarily use space efficiently. On the other hand, "plugging in" the next item to be stored in any available space can provide efficient use of the warehouse area but can cause problems in inventory and item location. As such, most prior art storage procedures require periodic inventory to correct errors in records or account for pilferage. Bar code systems currently provide a reasonably efficient method of conducting inventory but they still require the physical checking of pallets, packages, stacks, etc. Most prior inventory systems require restacking checked items to confirm the number of sub-units or boxed items in a particular batch. These labor intensive, prior art inventory techniques can be highly expensive to procure and time consuming to use properly.
Current security systems usually require the use of guards, electronic identification cards, combination locks, etc. to control personnel access to or egress from property. The use of coded cards and cipher locks, and the need to stop personnel to check their identification cards can decrease employee performance through inconvenience and loss of employee flexibility. When an employee needs to enter a new area, complex, time consuming security steps are usually required. At present, there is no inexpensive, easy method of learning who is present in a large area. Additionally, most property protection systems decouple the functions of security from those of personnel monitoring. Consequently, current personnel access systems are usually expensive to install, inconvenient to use, and difficult to maintain.
For industry and government, loss of property through pilferage, theft, and damage poses a major problem. To prevent removal of small items such as personal computers, heavy cables often anchor the items to desks, walls, or other large stationary objects. Although this approach is usually effective, it restricts rearranging office furniture, makes it difficult to exchange equipment and causes an unsightly appearance.
In most current systems for protecting warehouse inventory, stored items are easily inventoried, but items being removed are not easily monitored. Consequently, items often leave a warehouse without being detected. As mentioned above, this weakness often results from decoupling personnel monitoring and inventory monitoring. Prior art systems that address only one security problem are frequently circumvented, while those security systems that do work are usually inconvenient to use.
Bar coding has greatly improved the control of inventory at the point of sale. Items of a specific category can be deducted from stock, correct pricing ensured and errors in entry reduced. Shortcomings of such systems are the limited number of codes that can be put in the bar and the bar orientation requirement that the scanner see the bar. With the large number of products available on the market, the code limit is a significant problem. Also, anyone who has waited at a checkout as the cashier attempted to get a good scan can attest to the inconvenience of the marking-scanner alignment requirement.
In a problem related to retail pricing, admission or passage fees are presently collected using inconvenient or expensive techniques. Parkway or turnpike fees are often collected by stopping the car, collecting cash, providing change, and allowing the driver to proceed. This process often causes traffic jams during peak hours and higher tolls to pay toll collector salaries.
"Friendly fire" has been the cause of many losses during combat. The "fog" of war induced by adverse weather, obscurants, long stand-off ranges for weapon systems and actions while under stress often cause the inadvertent discharge of weapons against friendly units. Expensive Navy systems, such as aircraft and ships, use active interrogator identification of a "boggie" (unknown) before weapons are employed. However, no similar system is available for smaller objects, such as tanks, trucks, infantry fighting vehicles, and, perhaps most important, soldiers themselves. Some simple, prior art identification systems use thermal tape markings, light emitting diodes and other visual signals. These marking techniques are easily mimicked. Additionally, ground clutter and purposeful camouflage often prevent full employment of current and developing systems.